This invention relates to the palladium-catalyzed amination of conjugated dienes to produce long-chain unsaturated amines. More particularly, this invention relates to an improved method of separating the soluble homogeneous catalyst from the liquid products of the palladium-catalyzed amination reaction.
The use of homogeneous catalysts for various organic syntheses is well-known. For useful background information in this field, reference can be had to the following comprehensive publications:
C. W. Bird, "Transition Metal Intermediates in Organic Synthesis," Academic Press, New York, N.Y., 1967.
"Homogeneous Catalysis," Adv. in Chem. Series 70, Amer. Chem. Soc., Washington, D.C., 1968.
J. Tsuji, "Organic Synthesis by Means of Transition Metal Complexes," Springer-Verlag, New York, N.Y., 1975.
P. M. Maitlis, "The Organic Chemistry of Palladium, Vol. II," Academic Press, New York, N.Y., 1971.
In many instances, homogeneous catalysts perform syntheses which are impossible to effect with heterogeneous catalysts or outperform their heterogeneous counterparts in rate or selectivity. Despite their great usefulness, many homogeneous catalysts have a drawback in that they are difficult to separate from the products of the catalysis. An ideal situation would be a "heterogeneous-homogeneous" catalyst which somehow would retain the chemical advantages of the soluble homogeneous catalysts but which could also be easily separated from the liquid reaction products.
Recently, in said copending application Ser. No. 697,900, filed June 21, 1976; the present inventors disclosed an improved homogeneous catalyst system which gives high yields of N-(alkadienyl)amines by reaction of conjugated dienes with primary and secondary amines as well as with ammonia. Notwithstanding the decided advantages of this catalyst system, difficulty is encountered in many instances in separating the liquid product from the soluble catalyst. Therefore, it was desired to develop means for improving the separation procedure.